JPH09181759A - Method and apparatus for transmitting reception confirmation signal - Google Patents

Abstract

Kind Code: A1 The present invention relates to a method and device for returning a reception confirmation signal in a communication system that performs bidirectional communication via a digital network having a 1: n structure such as a CATV network. By transmitting via the communication channel, there is no collision with control messages of other terminals,
The purpose is to improve transmission efficiency. SOLUTION: In an uplink transmission frame, a reception confirmation signal channel for transmitting an uplink reception confirmation signal is provided separately from a control channel for transmitting an uplink control message, and a reception confirmation signal transmission section provided in each terminal device. An uplink reception confirmation signal is transmitted through the reception confirmation signal channel, and a reception confirmation signal receiving section provided in the center-side device receives the uplink reception confirmation signal through the reception confirmation signal channel. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reception confirmation signal returning method and a transmission device in a communication system for bidirectional communication via a network of 1: n structure such as a CATV network.

In recent years, a communication system has been developed which uses an existing CATV network and realizes interactive services such as a telephone service and a VOD (video on demand) service. When realizing such bidirectional communication, it is necessary to transmit control signals in both the up and down directions. But C
In a one-to-n configuration network such as an ATV network (for example, a tree-type network), in the upstream direction (terminal → center direction, n → 1 direction), control signals are simultaneously transmitted from a plurality of terminals to the center side. If they do, these control signals may collide. Therefore, collision control (a slotted aloha method or the like) is usually used in the up direction.

In a system in which a control signal is transmitted and received between a center and a terminal, a message may be lost due to a transmission error or the like. Therefore, an ACK signal (Acknowledge: reception confirmation signal) is returned when the message is received. ,
A method of confirming delivery is generally used. An example of this method is the transmission of an ACK signal by layer 2 of ISDN.

[0004]

2. Description of the Related Art FIG. 14 shows an example of a 1-to-n configuration network. FIG. 15 shows a conventional example of a center-side device in this network, and FIG. 16 shows a conventional example of a terminal device. Further, FIG. 17 shows a format of a transmission / reception frame between the center and the terminal in the conventional configuration. 18 is a flow chart showing an operation procedure in the conventional center side device, and FIG. 19 is a flow chart showing an operation procedure in the conventional terminal device.

The network shown in FIG. 14 shows the configuration of a communication system that provides a two-way telephone service via a 1-to-n digital network (CATV network in the example). In this communication system, the center-side device 1 is connected to an exchange 3 that provides a telephone exchange function, and an external mixer / demultiplexer 4 via a transmission line 6 and a relay amplifier 5 on the transmission line 6 are appropriately connected. Through a plurality of terminal devices 2
Connected to each other.

In FIG. 15, the center side device 1 is an exchange interface unit 11, a network unit 12, a transmission frame assembling unit 13, a reception frame disassembling unit 14, a transmission signal modulating unit 15, a reception signal demodulating unit 16, a CPU (central processing unit). ) 17, ROM (Read Only Memory) 18, RA
It is configured to include M (random access memory) 19 and the like.

The exchange interface unit 11 is an interface for connecting to the exchange 3 which provides a telephone exchange function, and the network unit 12 rearranges the call channels B on the exchange 3 side and the transmission line 6 side.

The call signal transmitted from the network unit 12 is input to the transmission frame assembling unit 13. A control signal or the like is input to the transmission frame assembling unit 13 from the CPU 17 side, and the transmission frame assembling unit 13 assembles the control signal and the call channel or the like into a transmission frame. This transmission frame is modulated by the transmission signal modulator 15 into a transmission format (modem signal) on the network, and is sent to the transmission path 6 side through the external mixer / demultiplexer 4.

On the other hand, the reception frame received from the transmission line 6 side through the external mixer / demultiplexer 4 is demodulated by the demodulation unit 16 from the transmission format (modem signal) on the network, and the reception frame decomposing unit. 14 is input. The reception frame disassembling unit 14 disassembles the reception frame into a speech channel, a control signal and the like. The decomposed speech channel is input to the network unit 12, and the data of the decomposed received frame is stored in the RAM 19.

Further, the center side device is provided with a CPU 17, a ROM 18 and a RAM 19 as main control parts,
The CPU 17 controls the center side device 1 as a whole, and
The OM 18 stores programs and the like, and the RAM 19 stores data such as received frames.

The RAM 19 also stores a transmission frame memory 191 and a reception frame memory 192. The transmission frame memory 191 stores maintenance data, control data, and a plurality of communication channel (B-ch) data, and receives a reception frame. The memory 192 stores maintenance data, control data, and a plurality of call channel data.

FIG. 15 shows the CPU 17 and the ROM 18
The function constituted by is represented by a functional block diagram. That is, the control message transmitting unit 171, the ACK signal receiving unit 172, the control message receiving unit 173, and the control message processing unit 174 are included. The control message receiving unit 173 retrieves the data decomposed by the reception frame decomposing unit 14 and stored in the reception frame memory 192 to receive the control message.
Reference numeral 71 sends the control message of the transmission frame to be assembled by the transmission frame assembling unit 13 to the frame assembling unit 13 via the transmission frame memory 191, and transmits the control message, and also activates the ACK signal reception timer when the reception of the control message is notified. The control message processing unit 174 performs processing such as termination processing of the control message received by the control message receiving unit 173 and generation of a control message to be sent to the control message transmitting unit 171. ACK signal receiver 1
72 checks whether the control message received by the control message receiving unit 173 is an ACK signal reception,
If the K signal is received, the stop instruction of the ACK signal reception timer is sent to the transmission message transmission unit 171.

In FIG. 16, the terminal device 2 includes a transmitting / receiving signal mixer / demultiplexer 21, a transmitting signal modulating unit 22, a receiving signal demodulating unit 23, a transmitting frame assembling unit 24, a receiving frame disassembling unit 25, and an external device. Interface unit 26, CPU
27, ROM 28, RAM 29 and the like.

The received modem signal from the transmission line 6 is input to the demodulation section 23 via the mixer / demultiplexer 21 for distributing the modem signal, and the demodulation section 23 transmits the received frame to the transmission format (modem signal) on the network. And demodulates and sends to the received frame disassembling unit 25. Received frame disassembling unit 25
Decomposes the received frame into speech channels and control signals,
The call channel is sent to an external device (for example, a telephone) via the external device interface unit 26, and the data of the decomposed received frame is stored in the RAM 29. The external device interface unit 26 interfaces with an external device.

Further, the signal from the external device interface section 26 is input to the transmission frame assembling section 24, and the transmission frame assembling section 24 assembles a transmission control signal, a speech channel and the like into a transmission frame and sends it to the modulation section 22. The modulator 22 modulates the transmission frame into a transmission format (modem signal) on the network and sends it to the transmission path 6 side through the mixer / distributor 21.

The terminal device 2 has a CPU 27, a ROM 28, and a RAM 29 as main parts for controlling the terminal device.
Etc. are provided.

The RAM 29 is a transmission frame memory 291,
The reception frame memory 292 is stored, the transmission frame memory 291 stores maintenance data, control data, and a plurality of communication channel data, and the reception frame memory 292 stores maintenance data, control data, and a plurality of communication channel data.

FIG. 16 is a functional block diagram showing the functions of the CPU 27 and the ROM 28. As shown in the figure, it comprises a control message transmitting section 271, an ACK signal transmitting section 272, a control message receiving section 273, a control message processing section 274 and the like. Control message receiving unit 27
3 is decomposed by the frame disassembling unit 25 and received frame memory
The control message is received by searching the data of the received frame stored in 92. The control message transmitting unit 271 sends the control message to be incorporated in the transmission frame by the frame assembling unit 24 to the frame assembling unit 24 via the raw frame memory 291 and transmits it. The control message processing unit 274 performs processing such as terminating the control message received from the control message receiving unit 273 and generating a control message to be transmitted by the control message transmitting unit 271. A
When the CK signal transmission unit 272 receives the control message, the A
The transmission message transmission unit 271 is instructed to transmit the CK signal.

Uplink / downlink transmission / reception data in this communication system is composed of a frame in which a plurality of speech channels are time-division multiplexed, and the format of each frame is shown in FIG. In FIG. 17, (1) shows the downlink frame format, and (2) shows the uplink frame format.

The frame format 7 of the downlink data stream from the center side to the terminal side is composed of a distance control channel 72, a control channel 71, and a plurality of communication channels Bn to Bo as shown in FIG. The control message 73 of the channel 71 includes the terminal ID of its own terminal, control data, and FCS (frame check sequence).

On the other hand, the frame format 8 of the upstream data string from the terminal side to the center side is, as shown in FIG. 17 (2), a distance control channel 84, a vacant area, a control channel 81, a plurality of speech channels Bo ... Consists of Bn,
The control message 83 of the control channel 81 includes a terminal ID, control data, and FCS.

Here, since the distance from the center to each terminal is different in each of the distance control channels 84, it is necessary to compensate for the difference in signal propagation time based on the difference in the distance. It is used to adjust the transmission timing based on the difference in distance. Further, an empty area after the distance control channel 84 of the upstream frame format is an area reserved for receiving a signal from a terminal for which distance control is not performed, is not normally used, and the terminal is It is initially installed and used only temporarily when measuring distances.

The operation of this conventional system is shown in FIGS.
9 will be described below. First, the operation of the center-side device 1 will be described with reference to the flowchart of FIG. When a control message transmission request (for example, an incoming signal of a telephone service) to the terminal device 2 is generated, the control message processing unit 174 transmits the control message to the control message transmission unit 171 (step S1). Upon receiving the control message, the control message transmitting unit 171 sends the control message to the frame assembling unit 13 via the transmission frame memory 191, incorporates the control message into the transmission frame, and sends the control message to the terminal device 2 via the downlink control channel 71. 73 is transmitted (step S2).

After this, the control message transmitting unit 171 sends A
The CK signal reception timer is started (step S3).
The control message receiving unit 173 has a reception frame memory 19
2 to retrieve the control message (step S
4) It is checked whether the control message is normally received (step S5). When the control message is normally received, the ACK signal receiving unit 172 checks whether this control message is an ACK signal from the destination terminal for the previously transmitted control message (step S).
6). If it is an ACK signal from the destination terminal, it notifies the control message transmitting section 171 that the control message transmitting section 171 stops the ACK signal reception timer activated at the time of transmitting the control message to the terminal (step S7). .

On the other hand, when the control message cannot be normally received (step S5) or when the control message is not the ACK signal, the control message transmitting unit 171 determines whether the ACK signal reception timer has expired. Check (step S8). If not expired,
The next control message received from the control message processing unit 174 is transmitted (step S9).

On the other hand, if it has expired, it is checked whether or not the number of times of retransmitting the control message corresponding to the expired ACK signal reception timer has reached the specified number or more (step S10). If it is less than the specified number of times, the control message transmission unit 171 retransmits the control message 73 corresponding to the expired ACK signal reception timer to the terminal device 2 via the downlink control channel 71 (step S11). If the number of times is equal to or more than the specified number of times, it is determined that the message transmission has failed, and the transmission of the control message is ended.

Next, the operation procedure in the terminal device 2 is shown in FIG.
This will be described below with reference to the flowchart of FIG. The control message receiving unit 273 of the terminal device 2 determines whether the control message 73 addressed to the own terminal is received by the reception frame memory 292.
Is searched for and recognized (step S21). When the control message addressed to the own terminal is received, the control message receiving unit 2
73 instructs the ACK signal transmitting unit 272 to transmit the ACK signal as the control message 83, and passes the received control message 33 to the control message processing unit 274 (step S22). The ACK signal transmitting unit 272 transmits the control message 83 as an ACK signal to the center-side communication device 1 via the control message transmitting unit 271 via the uplink control channel 81 (step S).
23).

[0028]

In the conventional bidirectional communication system, only one control channel is used in each of the upstream and downstream frames for transmitting and receiving the control message. In such a communication system, when transmitting a control message in the downlink direction (center → terminal), when the center side device transmits the control message to a plurality of terminals, the control message addressed to each terminal is transmitted over one control channel in a time-consuming manner. Since they are shifted and transmitted sequentially, and each terminal extracts the control message addressed to itself from the reception control message, only one control message is transmitted on the transmission path, and therefore the downlink control message is transmitted. Does not collide with control messages intended for other terminals. On the other hand, in the transmission of the control message in the up direction (terminal → center), if each terminal simultaneously transmits the control message in the up direction, the control messages may collide with each other.

Therefore, although the downlink ACK signal for the uplink control message does not collide, the uplink ACK signal for the downlink control message may collide with the uplink control message from another terminal. . When a collision occurs, both the colliding ACK signal and other uplink control messages are discarded. As a result, the original downlink control message that caused the ACK signal needs to be retransmitted, and the uplink control message that has collided also needs to be retransmitted, so that the control channel is congested and the transmission efficiency decreases. There was a problem.

For this reason, a method of not returning an ACK signal to the downlink control message is also conceivable, but in this method there is no confirmation of delivery, so the protocol becomes indeterminate and the state side and terminal side do not match. It is expected that failures such as lockups will occur.

Further, normally, an ACK signal is also transmitted to the uplink control message via the downlink control channel. For this reason, when another downlink control message is congested, the ACK signal is further added to the congested control message, so that the control channel is extremely congested and the transmission efficiency is reduced.

The present invention has been made in view of the above problems, and by transmitting the ACK signal via a dedicated communication channel, it is possible to eliminate the collision with the control message of another terminal and improve the transmission efficiency. With the goal.

[0033]

SUMMARY OF THE INVENTION The present invention relates to a reception confirmation signal transmission device in a communication system for bidirectional communication via a network of 1: n structure. According to one aspect of the present invention, in the uplink transmission frame, a reception confirmation signal channel for transmitting an uplink reception confirmation signal is provided separately from the control channel for transmitting the uplink control message, and the reception confirmation provided in each terminal device is provided. The signal transmission unit transmits an uplink reception confirmation signal via the reception confirmation signal channel, and the reception confirmation signal reception unit provided in the center-side device transmits the uplink reception confirmation signal via the reception confirmation signal channel. Receive a reception confirmation signal. By this means, it is possible to avoid a collision between the reception confirmation signal and the uplink control message from another terminal.

According to another aspect of the present invention, the reception confirmation signal channel is arranged in an empty area after the distance control channel. As a result, the channel can be effectively used.

According to still another aspect of the present invention, the reception confirmation signal transmission timing control section provided in the terminal device transmits the reception confirmation signal in the upstream direction in an upstream transmission frame after a lapse of a fixed time after reception of the downlink control message. To be transmitted. The downlink control message has a property of being transmitted one by one with a time shift even when addressed to a plurality of terminal devices. Therefore, even when a plurality of terminal devices transmit a reception confirmation signal, By transmitting at different timings, it is possible to avoid message collision on the reception confirmation signal channel.

In still another mode of the present invention, in each of the above modes, a downlink reception confirmation signal channel for transmitting a downlink reception confirmation signal separately from the control channel for transmitting the downlink control message in the downlink transmission frame. In the reception confirmation signal transmitting unit provided in the center side device, the downlink reception confirmation signal is transmitted via the downlink reception confirmation signal channel, and the reception confirmation signal receiving unit provided in each terminal device, A downlink reception confirmation signal is received via the downlink reception confirmation signal channel. By doing so, it becomes possible to send a control message to the terminal even during downlink reception confirmation transmission, and it is possible to improve the use efficiency of the control channel.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. The present embodiment is applied to a communication system that provides a two-way telephone service via a digital network of a CATV network having a 1: n structure as shown in FIG. FIG. 2 shows the configuration of a center-side device that performs a method of returning a reception confirmation signal as an embodiment of the present invention in the communication system, and FIG. 3 shows the configuration of a terminal device in the communication system. Further, FIG. 1 shows a format of a transmission / reception frame between a center and a terminal in the communication system. In FIG. 1, (1) is a downstream frame format, and (2) is an upstream frame format. Further, FIG. 4 is a flowchart showing an operation procedure in the center side device, and FIGS. 5 and 6 are flowcharts showing an operation procedure in the terminal device.

Here, the respective constituent parts in FIGS. 2 and 3 to which the same numbers as those explained in the conventional example of FIGS. 14 to 16 are given have the same functions as those explained in the conventional example. As a difference from the conventional example, as shown in FIG. 1B, a dedicated ACK channel 82 for transmitting an ACK signal is newly provided after the control channel 81 in the upstream frame format. There is. The ACK signal of the ACK channel 82 (also referred to as ACK message) is
ACK indicating the terminal ID of the terminal itself and ACK
It consists of data and FCS.

Further, in response to the provision of the ACK signal channel 82, RA in the center side device 1 of FIG.
Control ACK data for exclusively storing the ACK signal is added as data stored in the reception frame memory 192 in M19. Further, the ACK signal receiving unit 172 in the center side device 1 of FIG.
The contents of 2 can be directly searched to check the reception of the ACK signal, and when the ACK signal is received, the control message transmitting unit 171 is notified.

Similarly, the RAM in the terminal device 2 of FIG.
As the data stored in the transmission frame memory 291, the control ACK data for exclusively storing the ACK signal is added. Further, in the terminal device 2 of FIG. 3, the ACK signal transmitting unit 272 in the functional block diagram realized by the CPU 27, the ROM 28 and the like directly transmits the ACK signal instead of via the control message transmitting unit 271 as in the conventional case. The ACK signal can be sent to the center side device 1 by sending it to the transmission frame memory 291.

The ACK signal transmission timing control unit 2
75 may be newly provided. The ACK signal transmission timing unit 275 is used by the control message receiving unit 2
When the reception of the control message is notified from 73, it indicates the timing of transmitting the ACK signal for the received control message in the upstream frame after a certain timing from the reception of the downlink control message.

The operation of the system of this embodiment will be described below with reference to FIGS. First, the operation of the center-side device 1 will be described with reference to the flowchart of FIG. When a request to send a control message (for example, an incoming signal of a telephone service) to the terminal device 2 is generated, the control message processing unit 174 sends the control message to the control message sending unit 171.
(Step S30). When the control message transmitting unit 171 receives the control message, the control message transmitting unit 171 transmits the control message to the frame assembling unit 1 via the transmission frame memory 191.
3 and incorporates it into the transmission frame, and sends the control message 7 to the terminal device 2 via the downlink control channel 71.
3 is transmitted (step S31).

At this time, the control message transmitting unit 171 outputs A
Start the CK signal reception timer (step S3)
2). The ACK signal receiving unit 172 searches the control ACK data of the reception frame memory 192 to receive the ACK signal, determines whether the reception of the ACK signal is normal (step S34), and the ACK signal is normally received. If so, the control message transmission unit 171 is notified of this.
As a result, the control message transmitting unit 171 causes the ACK
The ACK signal reception timer started at the time of transmitting the control message to the terminal corresponding to the signal is stopped (step S
35).

On the other hand, when the ACK message is not normally received, the control message transmitting section 171 turns the AC
It is checked whether the K signal reception timer has expired (step S36). If it has not expired, the next control message received from the control message processing unit 174 is transmitted (step S37).

On the other hand, if it has expired, it is checked whether or not the number of times of retransmitting the control message corresponding to the expired ACK signal reception timer has reached a specified number or more (step S38). If it is less than the specified number of times, the control message transmission unit 171 retransmits the control message 73 corresponding to the expired ACK signal reception timer to the terminal device 2 via the downlink control channel 71 (step S39). When the number of times is equal to or more than the specified number of times (step S38), it is determined that the message transmission has failed, and the transmission of the control message ends.

Next, the operation procedure in the terminal device 2 will be described below. First, the ACK signal transmission timing control unit 27
The operation in the case where 5 is not provided will be described with reference to the flowchart in FIG. Control message receiving unit 27 of terminal device 2
3 searches the reception frame memory 292 to recognize whether the control message 73 addressed to the own terminal is received (step S41). When the control message addressed to your terminal is received,
The control message receiving unit 273 is the ACK signal transmitting unit 272.
The control message 83 as an instruction to send an ACK signal as a control message 83
To the control message processing unit 274 (step S4
2). The ACK signal transmitting unit 272 transmits the control message 83 as an ACK signal to the center side communication device 1 via the control message transmitting unit 271 via the uplink control channel 81 (step S43).

Next, the ACK signal transmission timing control unit 2
The operation when 75 is provided will be described with reference to the flowchart of FIG. Control message receiving unit 27 of terminal device 2
3 searches the received frame memory 292 to recognize whether or not the control message 73 addressed to its own terminal is received (step S50). When the control message addressed to your terminal is received,
The control message receiving unit 273 is the ACK signal transmitting unit 272.
The ACK signal transmission timing control unit 275 is instructed to transmit an ACK signal, and the received control message 33 is passed to the control message processing unit 274 (step S52).

The ACK signal transmission timing control section 275 monitors the arrival of the timing designated in advance (timing after the elapse of a fixed time from the reception of the control message) (step S52), and determines whether the designated timing has arrived (step S53). ). When the designated timing comes, the ACK signal transmission timing control unit 275 causes the ACK signal transmission unit 27 to
2 is instructed to return the ACK signal 83 (step S54). The ACK signal transmission unit 272 uses the AC
The control message 83 as the K signal is transmitted to the center side communication device 1 via the control message transmission unit 271 via the upstream control channel 81 (step S55).

As described above, the ACK signal transmission timing control unit 275 sends A to the control message in the upstream frame after a lapse of a certain time from the reception of the control message.
When the ACK signal transmission timing is determined so that the CK signal is inserted, since the downlink control message has the property of being transmitted in sequence one message at a time, the uplink ACK signal returned from each destination terminal is also transmitted in sequence. Therefore, it is possible to prevent the collision with the ACK signal from another terminal.

7 and 8 show another embodiment of the present invention. FIG. 7 shows the configuration of the center-side device in this embodiment, and FIG. 8 shows the format of a transmission / reception frame transmitted / received in this embodiment. In FIG. 8, (1) is the downlink frame format, and (2) is the uplink frame format.

The difference from the above embodiment is the insertion position of the ACK channel in the upstream frame format shown in FIG. 8 (2). That is, in this embodiment, A
The CK channel 82 is housed in an empty area behind the distance control channel 84. Correspondingly, in the configuration of the center side device 1 of FIG. 6, the data structure of the reception frame memory 192 in the RAM 19 is such that the control ACK data is stored before the control data.

As described above, this distance control channel 84
The vacant area after is an area reserved for receiving signals from terminals that are not subject to distance control and is not normally used.It is only temporarily installed when the terminal is initially installed and distance measurement is performed. Since this area is used for an ACK signal, it is considered that this area has almost no effect on the practical operation after the initial installation of the terminal. Therefore, by accommodating the ACK signal channel 82 in an empty area after the distance control channel 84, it is possible to effectively use the upstream transmission path.

9 to 13 show another embodiment of the present invention. In this embodiment, an ACK channel for accommodating an ACK signal is provided not only in the upstream frame but also in the downstream frame. FIG. 9 shows the configuration of the center side device in this embodiment, and FIG. 10 shows the configuration of the terminal device. Further, FIG. 11 shows a format of a transmission / reception frame between the center and the terminal. FIG.
Among them, (1) is a downstream frame format and (2) is an upstream frame format. FIG. 12 is a flow chart showing the operation procedure of the center side device in this embodiment, and FIG. 13 is a flow chart showing the operation procedure of the terminal device.

In this embodiment, as shown in FIG. 11 (2), in the upstream frame, the ACK channel for accommodating the ACK signal exclusively after the control channel 81, as in the first embodiment. 82 is provided. At the same time, as shown in FIG. 11 (1), an AKC channel 74 for accommodating an ACK signal returned from the center side to the terminal side is provided behind the control channel 71 also in the downlink frame. The ACK message accommodated in this AKC channel 74 is the terminal ID of its own terminal, AC
It consists of ACK data indicating that it is K and FCS.

Corresponding to the provision of the downlink ACK channel in this way, in the center side apparatus of FIG. 9, the transmission frame memory 191 is provided with a storage area for control ACK data and the ACK signal transmission section 175 is provided. ACK
A signal transmission waiting queue unit 176 is newly provided. ACK
The signal transmission waiting queue unit 176 returns ACK to the terminal side.
This is a part for queuing a plurality of signals, and sequentially instructs the ACK signal transmitting section 175 to transmit the queued ACK signals. The ACK signal transmitting unit 175 directly transmits the ACK signal instructed to be transmitted to the transmission frame memory 191, so that the ACK signal is transmitted to the terminal device. In addition, the ACK signal receiving unit 17
2 directly receives the ACK signal by directly searching the data stored in the reception frame memory 192.

Corresponding to the provision of the downlink ACK channel, in the terminal device of FIG. 10, the reception frame memory 292 is provided with a storage area for control ACK data, and the ACK signal receiving section 276 is newly provided. The ACK signal receiving unit 276 is configured to directly search the data stored in the reception frame memory 292 to receive the ACK signal. When the ACK signal is received, the control message transmitting unit 276 is provided. ACK to 271
It is designed to stop the signal reception timer.

The operation of the system of this embodiment will be described below. The procedure for returning the ACK signal in the upstream direction is the same as that described in the first embodiment (that is, the one described in the flow charts of FIGS. 4, 5, and 6), and therefore its description is omitted here. Only the procedure for returning the ACK signal in the direction will be described.

First, the operation of the terminal device 2 will be described with reference to the flowchart of FIG. Control message processing unit 2
When a request to send a control message to the center side device 1 (for example, a call signal of a telephone service) is issued, the 74 sends the control message to the control message sending unit 271 (step S70). Upon receiving the control message, the control message transmission unit 271 sends this control message to the frame assembling unit 24 via the transmission frame memory 291 and incorporates it into the transmission frame, and controls the center side device 1 via the upstream control channel 81. The message 85 is transmitted (step S71).

After this, the control message transmitting unit 271
Start the CK signal reception timer (step S7)
2). The ACK signal receiving unit 267 searches the control ACK data of the reception frame memory 292 to receive the ACK signal, determines whether the ACK signal is normally received (step S74), and the ACK signal is normally received. If so, the control message transmission unit 271 is notified of this.
As a result, the control message transmitter 271 receives the ACK.
ACK started when sending control message corresponding to signal
The signal reception timer is stopped (step S75).

On the other hand, when the ACK message is not normally received, the control message transmitting section 271 sends the AC
It is checked whether the K signal reception timer has expired (step S76). If it has not expired, the next control message received from the control message processing unit 274 is transmitted (step S77).

On the other hand, if it has expired, it is checked whether or not the number of times of retransmitting the control message corresponding to the expired ACK signal reception timer has reached a specified number or more (step S78). If it is less than the specified number of times, the control message transmitting unit 271 retransmits the control message 85 corresponding to the expired ACK signal reception timer to the center side device 1 via the upstream control channel 81 (step S79). . When the number of times is equal to or more than the specified number of times (step S78), it is determined that the message transmission has failed, and the transmission of the control message ends.

Next, the operation procedure of the center side device 1 will be described below with reference to the flowchart of FIG. The control message receiving unit 173 of the center side device 1 receives the control message 85 from the terminal device 2 in the frame memory 2
92 is retrieved and received (step S60). When the control message from the terminal is received, the control message receiving unit 173 instructs the ACK signal transmission waiting queue unit 175 to transmit the ACK signal 75 addressed to the terminal, and the received control message 85 is transmitted to the control message processing unit 174. (Step S61).

The ACK signal transmission waiting queue unit 175 has an AC
The K signal transmission unit 176 monitors whether the ACK signal is being transmitted (step S62). If the ACK signal transmission unit 176 has completed transmission, the ACK signal transmission waiting queue unit 175
If there is an ACK signal that has been queued, it instructs the ACK signal transmitting unit 176 to transmit the ACK signal that has been queued (step S63). ACK
The signal transmission unit 176 transmits the ACK signal 75 to the terminal device 2 via the downlink ACK signal channel 74 (step S64).

Various modifications are possible in carrying out the present invention. For example, the above embodiment is an example, and it is also possible to obtain better effects by using two or more of the above embodiments in combination.

[0065]

As described above, according to the present invention, the ACK signal for the downlink control message can be transmitted without colliding with the uplink control message from another terminal, and the transmission efficiency is lowered by the message retransmission control. It is possible to prevent Further uplink control message and ACK
By dividing the channels used for the signals, there is an effect of increasing the transmission efficiency of the control signal in the upstream direction.

Further, by accommodating the ACK signal channel for transmitting the ACK signal in the vacant area for distance control which is not used during normal operation, the transmission band can be effectively used.

By determining the transmission timing of the uplink ACK signal by taking advantage of the characteristic that the downlink control messages are transmitted one message at a time, the uplink ACK signal will not collide with the ACK signals from other terminals. AC
This has the effect of increasing the transmission efficiency of the K signal.

Further, a downlink control message and a downlink ACK
Separating the used channel from the signal has the effect of improving the transmission efficiency of the downlink control signal.

[Brief description of the drawings]

FIG. 1 is a diagram showing a format of a transmission / reception frame between a center and a terminal in an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a center-side device in an embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a terminal device according to an embodiment of the present invention.

FIG. 4 is a flowchart showing an operation procedure of the center side apparatus in the embodiment of the present invention.

FIG. 5 is a flowchart showing an operation procedure of the terminal device when there is no ACK signal transmission timing control unit in the embodiment of the present invention.

FIG. 6 is a flowchart showing an operation procedure of the terminal device when there is an ACK signal transmission timing control unit in the embodiment of the present invention.

FIG. 7 is a diagram showing a configuration of a center-side device according to another embodiment of the present invention.

FIG. 8 is a diagram showing a format of a transmission / reception frame between a center and a terminal in another embodiment of the present invention.

FIG. 9 is a diagram showing a configuration of a center-side device according to still another embodiment of the present invention.

FIG. 10 is a diagram showing a configuration of a terminal device according to still another embodiment of the present invention.

FIG. 11 is a diagram showing a format of a transmission / reception frame between a center and a terminal according to still another embodiment of the present invention.

FIG. 12 is a flowchart showing an operation procedure of a center side apparatus in still another embodiment of the present invention.

FIG. 13 is a flowchart showing an operation procedure of a terminal device according to still another embodiment of the present invention.

FIG. 14 is a diagram showing an example of a 1-n digital network.

FIG. 15 is a diagram showing a configuration of a center-side device of a conventional example.

FIG. 16 is a diagram showing a configuration of a conventional terminal device.

FIG. 17 is a diagram showing a format of a transmission / reception frame between a center and a terminal in a conventional example.

FIG. 18 is a flowchart showing an operation procedure of a conventional center-side device.

FIG. 19 is a flowchart showing an operation procedure of a conventional terminal device.

[Explanation of symbols]

 1 center side device 2 terminal device 3 switching device 4, 21 mixing / branching device 5 relay amplifier 6 transmission line 11 switching device interface part 12 network part 13, 24 sending frame assembling part 14, 25 receiving frame disassembling part 15, 22 transmission signal Modulator 16,23 Received signal demodulator 17,27 CPU 18,28 ROM 19,29 RAM 26 External device interface 171,271 Control message transmitter 172 ACK signal receiver 173,273 Control message receiver 174,274 Control Message processing unit 175, 272 ACK signal transmission unit 176 ACK signal transmission waiting queue unit 191, 291 Transmission frame memory 192, 292 Reception frame memory 275 ACK signal transmission timing control unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Maeda 1-21-1 Akebono-cho, Tachikawa-shi, Tokyo Within Fujitsu ACE Co., Ltd. Inside ASC Co., Ltd. (72) Inventor Yoshiki Morimoto 1-21-1 Akebonocho, Tachikawa-shi, Tokyo Inside Fujitsu ASC Co., Ltd.

Claims (8)

[Claims] 1. A method of transmitting a reception confirmation signal in a communication system for performing bidirectional communication via a network of 1: n structure, wherein an uplink is transmitted in an uplink transmission frame separately from a control channel for transmitting an uplink control message. A transmission method of a reception confirmation signal, wherein a reception confirmation signal channel for transmitting a reception confirmation signal in the direction is provided, and an uplink reception confirmation signal is transmitted through the reception confirmation signal channel. 2. The transmission method of a reception confirmation signal according to claim 1, wherein the reception confirmation signal channel is arranged in an empty area after the distance control channel. 3. The method of transmitting a reception confirmation signal according to claim 1, wherein the reception confirmation signal in the upstream direction is transmitted in an uplink transmission frame after a lapse of a fixed time from the reception of the downlink control message in each terminal. 4. A downlink reception confirmation signal channel for transmitting a downlink reception confirmation signal is provided in the downlink transmission frame separately from the control channel for transmitting the downlink control message,
The transmission method of a reception confirmation signal according to any one of claims 1 to 3, wherein the reception confirmation signal of the downlink direction is transmitted via the channel for the reception confirmation signal of the downlink direction. 5. A transmission device for a reception confirmation signal in a communication system for bidirectional communication via a network of 1: n structure, wherein an uplink transmission frame is provided separately from a control channel for transmitting an uplink control message. A reception confirmation signal channel for transmitting a reception confirmation signal in the direction is provided, and each terminal device is provided with a reception confirmation signal transmission unit for transmitting the reception confirmation signal in the upward direction via the reception confirmation signal channel. A transmission device for a reception confirmation signal, further comprising a reception confirmation signal receiving section for receiving an uplink reception confirmation signal via the reception confirmation signal channel. 6. The transmission device of a reception confirmation signal according to claim 5, wherein the reception confirmation signal channel is arranged in an empty area after the distance control channel. 7. The terminal device is provided with a reception confirmation signal transmission timing control unit, and the reception confirmation signal transmission timing control unit transmits the reception confirmation signal in the upstream direction to an uplink transmission frame after a lapse of a certain time from the reception of the downlink control message. 7. The device for transmitting a reception confirmation signal according to claim 5, wherein the transmission device is configured to transmit. 8. A downlink reception confirmation signal channel for transmitting a downlink reception confirmation signal is provided in the downlink transmission frame in addition to the control channel for transmitting the downlink control message, and the center side device is provided with the downlink reception confirmation signal. A reception confirmation signal transmitting unit that transmits a reception confirmation signal in the downlink direction via the signal channel is provided, and reception confirmation is performed in which each terminal device receives the reception confirmation signal in the downlink direction via the channel for the downlink reception confirmation signal. The transmission device of the reception confirmation signal according to claim 5, further comprising a signal receiving unit.